The present invention relates to waterbed mattresses.
A problem with conventional waterbed mattresses is that the user does not really sleep on water. Rather, the user sleeps on polymeric material. Waterbed mattresses typically are made of an envelope having a top wall, a bottom wall, and side walls formed of a polymeric material such as polyvinylchloride. Other polymeric materials that have been suggested include polyethylene.
Mattresses are generally filled with water to about their design capacity, the depth of the water being from 8 to 9 inches. The amount of water placed in the mattress controls the "firmness" of the mattress.
When a person lies on the mattress, the top wall becomes taut and has high tension. Although the user believes he is sleeping on water, the dominant effect is produced by the taut top wall of the mattress. Although such a waterbed is more comfortable for many persons than a conventional box spring and mattress, the user is really not "floating" on water. It is believed that the lack of comfort resulting from the taut top wall has prevented some persons from using a waterbed.
Another problem with available waterbed designs is that the mattress itself has limited aesthetic appeal in the showroom. It is usually no more than flat, stretched piece of vinyl material which may have wrinkles on its top surface. This is in sharp contrast to the aesthetically pleasing and textured surface provided by the fabric on conventional mattresses. Since waterbed mattresses and conventional mattresses are often sold side-by-side in retail outlets, this is a significant competitive disadvantage for waterbed mattresses.
Another problem with available waterbed designs is how to accommodate couples of greatly different weights. When two persons of greatly different weights are on a waterbed mattress, often the heavier person forces so much of the water to the other side of the mattress that the lighter person is lying on a bulge. Another problem occurs where the persons sharing a waterbed mattress desire different firmness from the sleeping surface. To accommodate couples of different weight or couples desiring different firmnesses, there are available small size mattresses that can be placed in a single frame side-by-side. However, these side-by-side mattresses are more expensive than a single mattress, inconvenient to install, and invariably have a small gap between them.